1. Field of the Invention
In steel fabrication a contemporary problem is the drilling of rivet holes in steel, I-beams, columns and the like. Conventionally, the holes are first chalk marked, tapped or punched and then individually hand drilled. This is an extremely time consuming and costly process with labor costs currently at $5.00 to $8.00 per hour. Since the holes are measured and drilled manually without especial drill supporting devices, the incidence of error in hole placement is the rule rather than the exception.
Several elaborate multiple drilling head devices have been devised for handling I-beams. However, the gigantic size of these devices and their complex drill bit adjusting mechanisms require investment in the amounts of hundreds of thousands of dollars per multiple head installation.
2. Description of the Prior Art
LASSITER 1,027,347 Class 77/24, HALEY 3,501,982 Class 77/24, HALEY 3,529,496 Class 77/24.